1. Field of the Invention
The present invention relates to an air conditioner for automobiles, having a compressor adapted to be driven by the automobile engine, a condenser connected to the high-pressure side of the compressor and an evaporator connected to the low-pressure side of the compressor.
2. Description of the Prior Art
The air conditioner for automobiles usually has a refrigeration cycle constituted by a compressor adapted to be driven by the automobile engine, a condenser, a liquid tank, an orifice means such as an expansion valve and an evaporator. The air conditioner further has a radiator fan for use in combination with the condenser, and also a blower for the evaporator and so on.
Among these constituents of the air conditioner, the compressor, condenser, liquid tank and the radiator are disposed in the engine room, while the evaporator and the blower are disposed in the passenger's compartment of the automobile.
In air conditioners for automobiles, the temperature in the passenger's compartment is adjusted automatically by an on-off control of the compressor. Namely, when the measured temperature in the passenger's compartment has become a predetermined temperature, the compressor is turned operative to start the refrigeration cycle thereby to lower the temperature, while, when the temperature has become lower than another predetermined temperature, the compressor is automatically turned off to stop the refrigeration cycle thereby to recover the temperature.
Thus, in the prior art air conditioners, the compressor is turned operative and inoperative in accordance with the result of detection of the temperature solely, regardless of the running condition of the automobile.
On the other hand, the rate of increase of the fuel consumption due to the driving of the compressor varies depending on the running states of the automobile.
For instance, when the automobile is running at a constant speed of, for example, 40 Km/hr, the rate of fuel consumption (l/hr) is increased by about 20% due to the driving of the compressor. However, when the state of the engine braking for decelerating or stopping the automobile, the fuel consumption rate is not changed independently of whether the compressor is operating or not. Namely, when the automobile is being decelerated or stopped by the engine braking, a part of the kinetic energy possessed by the mass of the automobile is used for driving the compressor. In other words, the compressor produces a resistance which in turn acts as a part of the braking force.
In the prior art air conditioners, however, the operation of the compressor is controlled in accordance with the result of detection of the temperature in the passenger's compartment solely, as stated before. In such air conditioners, therefore, it is impossible to make efficient use of the kinetic energy of the automobile as the driving energy for driving the compressor of the air conditioner. Namely, it is not possible to reduce the fuel consumption rate of the engine for driving the compressor through efficient use of the kinetic energy of the automobile.